Method And System For All-Conductive Battery Electrodes

ABSTRACT

Systems and methods for all-conductive battery electrodes may include an electrode coating layer on a current collector, where the electrode coating layer comprises more than 50% silicon, and where each material in the electrode has a resistivity of less than 100 Ω-cm. The silicon may have a resistivity of less than 10 Ω-cm, less than 1 Ω-cm, or less than 1 mΩ-cm. The electrode coating layer may comprise pyrolyzed carbon and/or conductive additives. The current collector comprises a metal foil. The metal current collector may comprise one or more of a copper, tungsten, stainless steel, and nickel foil in electrical contact with the electrode coating layer. The electrode coating layer comprises more than 70% silicon. The electrode may be in electrical and physical contact with an electrolyte. The electrolyte may comprise a liquid, solid, or gel. The battery electrode may be in a lithium ion battery.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

N/A

FIELD

Aspects of the present disclosure relate to energy generation andstorage. More specifically, certain embodiments of the disclosure relateto a method and system for all-conductive battery electrodes.

BACKGROUND

Conventional approaches for battery electrodes may cause electrodecoating layer to lose contact with the electrode.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present disclosureas set forth in the remainder of the present application with referenceto the drawings.

BRIEF SUMMARY

A system and/or method for all-conductive battery electrodes,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentdisclosure, as well as details of an illustrated embodiment thereof,will be more fully understood from the following description anddrawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram of a battery with a silicon-dominant anode, inaccordance with an example embodiment of the disclosure.

FIG. 2 illustrates an anode during lithiation, in accordance with anexample embodiment of the disclosure.

FIG. 3 is a flow diagram of a process for fabricating cells, inaccordance with an example embodiment of the disclosure.

FIG. 4 illustrates an all-conductive electrode, in accordance with anexample embodiment of the disclosure.

FIG. 5. Illustrates an electrode with separated electrode coating layer,in accordance with an example embodiment off the disclosure.

FIG. 6 Illustrates an all-conductive electrode with separated electrodecoating layer, in accordance with an example embodiment off thedisclosure.

DETAILED DESCRIPTION

FIG. 1 is a diagram of a battery with silicon-dominant anodes, inaccordance with an example embodiment of the disclosure. Referring toFIG. 1, there is shown a battery 100 comprising a separator 103sandwiched between an anode 101 and a cathode 105, with currentcollectors 107A and 107B. There is also shown a load 109 coupled to thebattery 100 illustrating instances when the battery 100 is in dischargemode. In this disclosure, the term “battery” may be used to indicate asingle electrochemical cell, a plurality of electrochemical cells formedinto a module, and/or a plurality of modules formed into a pack.Furthermore, the cell shown in FIG. 1 is a very simplified examplemerely to show the principle of operation of a lithium ion cell.Examples of realistic structures is shown to the right in FIG. 1, wherestacks of electrodes and separators are utilized, with electrodecoatings typically on both sides of the current collectors. The stacksmay be formed into different shapes, such as a coin cell, cylindricalcell, or prismatic cell, for example.

The development of portable electronic devices and electrification oftransportation drive the need for high performance electrochemicalenergy storage. Small-scale (<100 Wh) to large-scale (>10 KWh) devicesprimarily use lithium-ion (Li-ion) batteries over other rechargeablebattery chemistries due to their high-performance.

The anode 101 and cathode 105, along with the current collectors 107Aand 107B, may comprise the electrodes, which may comprise plates orfilms within, or containing, an electrolyte material, where the platesmay provide a physical barrier for containing the electrolyte as well asa conductive contact to external structures. In other embodiments, theanode/cathode plates are immersed in electrolyte while an outer casingprovides electrolyte containment. The anode 101 and cathode areelectrically coupled to the current collectors 107A and 1078, whichcomprise metal or other conductive material for providing electricalcontact to the electrodes as well as physical support for the electrodecoating layer in forming electrodes.

The configuration shown in FIG. 1 illustrates the battery 100 indischarge mode, whereas in a charging configuration, the load 107 may bereplaced with a charger to reverse the process. In one class ofbatteries, the separator 103 is generally a film material, made of anelectrically insulating polymer, for example, that prevents electronsfrom flowing from anode 101 to cathode 105, or vice versa, while beingporous enough to allow ions to pass through the separator 103.Typically, the separator 103, cathode 105, and anode 101 materials areindividually formed into sheets, films, or electrode coating layercoated foils. Sheets of the cathode, separator and anode aresubsequently stacked or rolled with the separator 103 separating thecathode 105 and anode 101 to form the battery 100. In some embodiments,the separator 103 is a sheet and generally utilizes winding methods andstacking in its manufacture. In these methods, the anodes, cathodes, andcurrent collectors (e.g., electrodes) may comprise films.

In an example scenario, the battery 100 may comprise a solid, liquid, orgel electrolyte. The separator 103 preferably does not dissolve intypical battery electrolytes such as compositions that may comprise:Ethylene Carbonate (EC), Fluoroethylene Carbonate (FEC), PropyleneCarbonate (PC), Dimethyl Carbonate (DMC), Ethyl Methyl Carbonate (EMC),Diethyl Carbonate (DEC), etc. with dissolved LiBF₄, LiAsF₆, LiPF₆, andLiClO₄ etc. The separator 103 may be wet or soaked with a liquid or gelelectrolyte. In addition, in an example embodiment, the separator 103does not melt below about 100 to 120° C., and exhibits sufficientmechanical properties for battery applications. A battery, in operation,can experience expansion and contraction of the anode and/or thecathode. In an example embodiment, the separator 103 can expand andcontract by at least about 5 to 10% without failing, and may also beflexible.

The separator 103 may be sufficiently porous so that ions can passthrough the separator once wet with, for example, a liquid or gelelectrolyte. Alternatively (or additionally), the separator may absorbthe electrolyte through a gelling or other process even withoutsignificant porosity. The porosity of the separator 103 is alsogenerally not too porous to allow the anode 101 and cathode 105 totransfer electrons through the separator 103.

The anode 101 and cathode 105 comprise electrodes for the battery 100,providing electrical connections to the device for transfer ofelectrical charge in charge and discharge states. The anode 101 maycomprise silicon, carbon, or combinations of these materials, forexample. Typical anode electrodes comprise a carbon material thatincludes a current collector such as a copper sheet. Carbon is oftenused because it has excellent electrochemical properties and is alsoelectrically conductive. Anode electrodes currently used in rechargeablelithium-ion cells typically have a specific capacity of approximately200 milliamp hours per gram. Graphite, the electrode coating layer usedin most lithium ion battery anodes, has a theoretical energy density of372 milliamp hours per gram (mAh/g). In comparison, silicon has a hightheoretical capacity of 4200 mAh/g. In order to increase volumetric andgravimetric energy density of lithium-ion batteries, silicon may be usedas the electrode coating layer for the cathode or anode. Silicon anodesmay be formed from silicon composites, with more than 50% silicon, forexample.

In an example scenario, the anode 101 and cathode 105 store the ion usedfor separation of charge, such as lithium. In this example, theelectrolyte carries positively charged lithium ions from the anode 101to the cathode 105 in discharge mode, as shown in FIG. 1 for example,and vice versa through the separator 105 in charge mode. The movement ofthe lithium ions creates free electrons in the anode 101 which creates acharge at the positive current collector 1078. The electrical currentthen flows from the current collector through the load 109 to thenegative current collector 107A. The separator 103 blocks the flow ofelectrons inside the battery 100, allows the flow of lithium ions, andprevents direct contact between the electrodes.

While the battery 100 is discharging and providing an electric current,the anode 101 releases lithium ions to the cathode 105 via the separator103, generating a flow of electrons from one side to the other via thecoupled load 109. When the battery is being charged, the oppositehappens where lithium ions are released by the cathode 105 and receivedby the anode 101.

The materials selected for the anode 101 and cathode 105 are importantfor the reliability and energy density possible for the battery 100. Theenergy, power, cost, and safety of current Li-ion batteries need to beimproved in order to, for example, compete with internal combustionengine (ICE) technology and allow for the widespread adoption ofelectric vehicles (EVs). High energy density, high power density, andimproved safety of lithium-ion batteries are achieved with thedevelopment of high-capacity and high-voltage cathodes, high-capacityanodes and functionally non-flammable electrolytes with high voltagestability and interfacial compatibility with electrodes. In addition,materials with low toxicity are beneficial as battery materials toreduce process cost and promote consumer safety.

The performance of electrochemical electrodes, while dependent on manyfactors, is largely dependent on the robustness of electrical contactbetween electrode particles, as well as between the current collectorand the electrode particles. The electrical conductivity of siliconanode electrodes may be manipulated by incorporating conductiveadditives with different morphological properties. Carbon black(SuperP), vapor grown carbon fibers (VGCF), and a mixture of the twohave previously been incorporated separately into the anode electroderesulting in improved performance of the anode. The synergisticinteractions between the two carbon materials may facilitate electricalcontact throughout the large volume changes of the silicon anode duringcharge and discharge.

State-of-the-art lithium-ion batteries typically employ agraphite-dominant anode as an intercalation material for lithium. Withdemand for lithium-ion battery performance improvements such as higherenergy density and fast-charging, silicon is being added as an electrodecoating layer or even completely replacing graphite as a dominant anodematerial. Most electrodes that are considered “silicon anodes” in theindustry are graphite anodes with silicon added in small quantities(typically <20%). These graphite-silicon mixture anodes must utilize thegraphite, which has a lower lithiation voltage compared to silicon; thesilicon has to be nearly fully lithiated in order to utilize thegraphite. Therefore, these electrodes do not have the advantage of asilicon or silicon composite anode where the voltage of the electrode issubstantially above 0V vs Li/Li+ and thus are less susceptible tolithium plating. Furthermore, these electrodes can have significantlyhigher excess capacity on the silicon versus the opposite electrode tofurther increase the robustness to high rates.

Silicon-based anodes have a lithiation/delithiation voltage plateau atabout 0.3-0.4V vs. Li/Li+, which allows it to maintain an open circuitpotential that avoids undesirable Li plating and dendrite formation.While silicon shows excellent electrochemical activity, achieving astable cycle life for silicon-based anodes is challenging due tosilicon's large volume changes during lithiation and delithiation.Silicon regions may lose electrical contact from the anode as largevolume changes coupled with its low electrical conductivity separate thesilicon from surrounding materials in the anode.

In addition, the large silicon volume changes exacerbate solidelectrolyte interphase (SEI) formation, which can further lead toelectrical isolation and, thus, capacity loss. Expansion and shrinkageof silicon particles upon charge-discharge cycling causes pulverizationof silicon particles, which increases their specific surface area. Asthe silicon surface area changes and increases during cycling, SEIrepeatedly breaks apart and reforms. The SEI thus continually builds uparound the pulverizing silicon regions during cycling into a thickelectronic and ionic insulating layer. This accumulating SEI increasesthe impedance of the electrode and reduces the electrode electrochemicalreactivity, which is detrimental to cycle life.

The silicon source for fabricating silicon-dominant anodes is importantto cell performance. In this disclosure, silicon-dominant anodes withhigher impurity levels, which impact anode resistivity and SEIformation, and with conductive pyrolyzed binder material result inincreased cell capacity retention. In conventional silicon anodes, whichare typically graphite anodes with silicon added up to about 20%, thebinder is non-conductive upon pyrolysis. Example binder materials inthese electrodes are styrene butadiene rubber (SBR) or carboxymethylcellulose (CMC). For such materials, conductive additives are needed toincrease electrode conductivity, but this requires enough additive thatthe conductive material is close enough to tunnel across thenon-conductive pyrolyzed binder, meaning there is less binder materialby weight. For the direct coated, or continuous electrodes, describedhere, the binder material is conductive after pyrolysis, which inconjunction with the higher impurity level and thus higher conductivitysilicon results in an all-conductive electrode.

FIG. 2 illustrates an anode during lithiation, in accordance with anexample embodiment of the disclosure. Referring to FIG. 2, there areshown a current collector 201 and an electrode coating layer 205. Thelayer thicknesses are not necessarily shown to scale In an examplescenario, the anode electrode coating layer 205 comprises siliconparticles in a binder material and a solvent, where the electrodecoating layer is pyrolyzed to turn the binder into a conductive carbonthat provides a structural framework around the silicon particles andalso provides electrical conductivity. The electrode coating layer 205may comprise active material that is utilized in thelithiation/delithiation process and other materials such as pyrolyzedbinder, conductive additives, etc.

The current collector 201 may comprise a metal film, such as copper,nickel, or titanium, for example, although other conductive foils may beutilized depending on desired tensile strength. The current collector201 may comprise electrode perforations formed therein to allowlithiation to pass through from the side of the current collector 201opposite to the electrode coating layer 205. The electrode coating layer205 may be on both sides of the current collector 201.

FIG. 2 also illustrates lithium ions impinging upon and lithiating theelectrode coating layer 205 when incorporated into a cell with acathode, electrolyte, and separator (not shown). The lithiation ofsilicon-dominant anodes causes expansion of the material, wherehorizontal expansion is represented by the x and y axes, and thicknessexpansion is represented by the z-axis, as shown. The current collector201 has a thickness t, where a thicker foil provides greater strengthand providing the bond with the electrode coating layer 205 is strongenough, restricts expansion in the x- and y-directions, resulting ingreater z-direction expansion, thus anisotropic expansion. Examplethicker foils may be greater than 10 μm thick, such as 20 μm for copper,for example, while thinner foils may be less than 10 μm, such as 5-6 μmthick for copper.

The electrode coating layer 205 may comprise conductive silicon andpyrolyzed binder material, resulting in an all-conductive electrode.This is shown further with respect to FIGS. 3-6.

FIG. 3 is a flow diagram of a direct coating process for fabricating acell, in accordance with an example embodiment of the disclosure. Thisprocess comprises physically mixing the electrode coating layer,conductive additive, and binder together, and coating it directly on acurrent collector. This example process comprises a direct coatingprocess in which an anode or cathode slurry is directly coated on acopper foil using a binder such as Sodium Alginate, PAI, PI and mixturesand combinations thereof.

In step 301, the raw electrode electrode coating layer may be mixedusing a binder/resin (such as PI, PAI), solvent, and conductive carbon.For example, for the anode, graphene/VGCF (1:1 by weight) may bedispersed in NMP under sonication for, e.g., 1 hour followed by theaddition of Super P (1:1:1 with VGCF and graphene) and additionalsonication for, e.g., 45-75 minutes. Silicon powder with a desiredparticle size and impurity level, as discussed with respect to Table 1below, may then be dispersed in polyamic acid resin (15% solids inN-Methyl pyrrolidone (NMP)) at, e.g., 800-1200 rpm in a ball miller fora designated time, and then the conjugated carbon/NM P slurry may beadded and dispersed at, e.g., 1800-2200 rpm for, e.g., anotherpredefined time to achieve a slurry viscosity within 2000-4000 cP and atotal solid content of about 30%. The particle size and mixing times maybe varied to configure the electrode coating layer density and/orroughness. Furthermore, cathode electrode coating layers may be mixed instep 301, where the electrode coating layer may comprise lithium cobaltoxide (LCO), lithium iron phosphate, lithium nickel cobalt manganeseoxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithiummanganese oxide (LMO), lithium nickel manganese spinel, or similarmaterials or combinations thereof, mixed with a binder as describedabove for the anode electrode coating layer.

In step 303, the anode or slurry may be coated on a current collectorsuch as a copper foil. Similarly, cathode electrode coating layers maybe coated on a foil material, such as aluminum, for example. In oneembodiment, the foil may comprise perforations through the material toallow flow-through of lithiation during operation of the cell.

The electrode coating layer may undergo a drying in step 305 resultingin less than 20% residual solvent content. An optional calenderingprocess may be utilized in step 305 where a series of hard pressurerollers may be used to finish the film/substrate into a smoother anddenser sheet of material. In step 307, the foil and coating proceedsthrough a roll press for lamination. Steps 303 and 305 may be repeatedto coat both sides of the current collector.

In step 309, the electrode coating layer may be pyrolyzed by heating to500-800° C. such that carbon precursors are partially or completelyconverted into conductive carbon. The pyrolysis step may result in ananode electrode coating layer having silicon content greater than orequal to 50% by weight, where the anode has been subjected to heating ator above 400 degrees Celsius. The binder material is conductive afterpyrolysis, so along with the conductive silicon and conductiveadditives, the electrode is all-conductive. And native oxides formed onthe silicon and/or metal foil are thin enough that electrons easilytunnel.

Pyrolysis can be done either in roll form or after punching in step 311.If done in roll form, the punching is done after the pyrolysis process.In instances where the current collector foil is notpre-punched/pre-perforated, the formed electrode may be perforated witha punching roller, for example. The punched electrodes may then besandwiched with a separator and electrolyte to form a cell. In step 313,the cell may be subjected to a formation process, comprising initialcharge and discharge steps to lithiate the anode, with some residuallithium remaining, and the cell capacity may be assessed. Theperforations in the electrodes allows lithium to flow from double-sidedcathodes to anodes even if one side of the cathode does not face ananode, thereby increasing cell capacity.

FIG. 4 illustrates an all-conductive electrode, in accordance with anexample embodiment of the disclosure. Referring to FIG. 4, there isshown electrode 400 comprising a current collector 401 and electrodecoating layer 405. There is also shown length and width dimensions L andW, which in this example are the same for both the layers, although thisis not necessarily the case. In addition, thicknesses t_(ac) and t_(cc)are shown for the electrode coating layer 405 and current collector 401,respectively. The electrode coating layer 405 may be on both sides ofthe current collector 401.

A simplified equivalent circuit is shown to the right of the electrode400, showing the resistances of the layers, Rac for the resistance ofthe electrode coating layer 405 and R_(cc) for the current collector 401between an external lead of the current collector 401 and theelectrolyte 409. The resistance of a slab of material with thedimensions shown is defined by the relation R=ρ*(L/W*t), where ρ is theresistivity of the layer in ohm-cm. Similarly, the sheet resistance ofeach layer is its ρ/t. Typical resistivities for current collectormaterials are ˜1.7×10⁻⁶ Ω-cm for copper, ˜2.6×10⁻⁶ Ω-cm for aluminum,5.6×10⁻⁶ Ω-cm for tungsten, and ˜6.9×10⁻⁵ Ω-cm for stainless steel.

The impurity level of the silicon may be configured such that theresistivity of the silicon in the electrode coating layer is less than˜100 Ω-cm, for example. In another example scenario, the resistivity ofthe silicon may be less than ˜10 Ω-cm, less than ˜1 Ω-cm, less than 0.1Ω-cm, less than 10 mΩ-cm, and in yet another example scenario, theresistivity may be less than 1 mΩ-cm. If the electrode coating layer iselemental silicon with impurities, as opposed to SiO_(x) used inconventional electrodes, the resistivity is much lower.

Furthermore, the binder material used for the electrode coating layer isconductive after pyrolysis. For example, carbonized PI may have aresistivity of less than 100 Ω-cm, less than 1 Ω-cm, or less than 10mΩ-cm, for example, depending on pyrolysis temperature. Similarly,carbonized PAI may have a resistivity of less than 10 Ω-cm, less than0.1 Ω-cm, or less than 1 mΩ-cm, for example, depending on pyrolysistemperature. In addition, conductive additives may be included in theelectrode coating layer, further decreasing the resistivity, althoughwithout requiring a density of additives to cause the pyrolyzed binderto be conductive via tunneling as is needed in conventional electrodes.

An all-conductive electrode may improve cell capacity retention byreducing the capacity loss from portions of electrode coating layerbreaking off due to cycling expansion/contraction duringlithiation/delithiation. In conventional electrodes where the silicon isnot conductive, such as with high purity silicon or SiO_(x), anymaterial that separates from the electrode coating layer slab althoughstill in contact, will have a voltage drop between it and the remainingelectrode coating layer, such that lithiation may occur and then becometrapped as the potential drop of the separated material is such that itdoes not get to a delithiation voltage during operation. This isillustrated further with respect to FIGS. 5 and 6.

FIG. 5. Illustrates an electrode with separated electrode coating layer,in accordance with an example embodiment off the disclosure. Referringto FIG. 5, there is shown an electrode 500 with current collector 501and electrode coating layer 505. There is also shown separated electrodecoating layer 511, that has cracked off of the electrode coating layer505 due to expansion and contraction during lithiation/delithiation, forexample. The size and shape of the separated material 511 is just asimple example for illustration purposes, and may actually extend allthe way across the width or length, through the full thickness of theelectrode coating layer 505, or may be small sections distributedthroughout the top surface, for example. The electrode coating layer 505may be on both sides of the current collector 501.

In the example scenario of FIG. 5, the electrode coating layer 505 maycomprise conventional materials where the binder is non-conductivefollowing pyrolysis and/or any silicon in the electrode coating layer505 comprises SiO_(x) or is higher purity, such that the resistivity issignificantly higher than the conductive materials in the electrodecoating layer 505. For example, the silicon may be over 100 Ω-cm, or maybe two orders of magnitude higher resistivity than the conductivematerial. In this example, there will be a voltage drop from theelectrode coating layer 505 to the separated electrode coating layer511, as illustrated by the potential difference between these layers andthe electrolyte 509. In an example scenario, this voltage drop may be˜0.5V. During lithiation, both the electrode coating layer 505 andseparated electrode coating layer 511 may not be lithiated causing thetotal capacity of the electrode to drop and thus potentially reducingthe capacity of the cell. If the separated electrode coating layer hasbeen lithiated, but due to the potential drop of the separated electrodecoating layer 511, it may not reach a potential where it can delithiateduring delithiation, thereby trapping lithium and reducing the capacityof the cell.

FIG. 6 Illustrates an all-conductive electrode with separated electrodecoating layer, in accordance with an example embodiment off thedisclosure. Referring to FIG. 6, there is shown an electrode 600 withcurrent collector 601 and electrode coating layer 605. There is alsoshown separated electrode coating layer 611, that has cracked off of theelectrode coating layer 605 due to expansion and contraction duringlithiation/delithiation, for example. The size and shape of theseparated material 611 is just a simple example for illustrationpurposes, and may actually extend all the way across the width orlength, through the full thickness of the electrode coating layer 605,or may be small sections distributed throughout the top surface, forexample. The electrode coating layer 605 may be on both sides of thecurrent collector 601.

In the example scenario of FIG. 6, the electrode coating layer 505 maycomprise all low resistivity materials, where the binder is conductivefollowing pyrolysis and the silicon in the electrode coating layer 605comprises higher levels of impurity, such that the conductivity issimilar to the other conductive materials in the electrode coating layer505. For example, the resistivity of the silicon may be under 100 Ω-cm,less than 1 Ω-cm, less than 0.1 Ω-cm, 10 mΩ-cm, and in yet anotherexample scenario, the resistivity may be less than 1 mΩ-cm. In theseexamples, there will be a much smaller voltage drop between theelectrode coating layer 605 and the separated electrode coating layer611, in contrast to the example of FIG. 5. In an example scenario, thevoltage drop may be ˜0.05V, as compared to the 0.5 V example of theelectrode in FIG. 5. It should be noted that these voltage differencesare merely examples and depend on the type of electrode coating layerand resistivities of the component materials.

The reduced potential difference is illustrated by the potentialdifference between these layers and the electrolyte 609 above theelectrode 600 in FIG. 6. During lithiation, both the electrode coatinglayer 605 and the separated electrode coating layer 611 are lithiated,and since the potential drop of the separated electrode coating layer611 is small, it still reaches a potential where it can significantly orcompletely delithiate, thereby retaining more of the capacity of thecell, even with the separation/pulverization of electrode coating layerdue to expansion and contraction. In this case, the effect of thevoltage drop will be much less compared to the effect shown in theexample of the electrode in FIG. 5.

In an example embodiment of the disclosure, a method and system isdescribed for all-conductive battery electrodes. The battery electrodemay comprise an electrode coating layer on a current collector, wherethe electrode coating layer comprises more than 50% silicon, and whereeach material in the electrode has a resistivity of less than 100 Ω-cm.The silicon may have a resistivity of less than 10 Ω-cm, less than 1Ω-cm, or less than 1 mΩ-cm. The electrode coating layer may comprise apyrolyzed carbon and/or conductive additive. The current collectorcomprises a metal foil. The metal current collector may comprise acopper, tungsten, stainless steel, or nickel foil or a combination ofthese metals (e.g., clad or plated) in electrical contact with theelectrode coating layer. The electrode coating layer comprises more than70% silicon. The electrode may be in electrical and physical contactwith an electrolyte. The electrolyte may comprise a liquid, solid, orgel. The battery electrode may be in a lithium ion battery.

As utilized herein, “and/or” means any one or more of the items in thelist joined by “and/or”. As an example, “x and/or y” means any elementof the three-element set {(x), (y), (x, y)}. In other words, “x and/ory” means “one or both of x and y”. As another example, “x, y, and/or z”means any element of the seven-element set {(x), (y), (z), (x, y), (x,z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one ormore of x, y and z”. As utilized herein, the term “exemplary” meansserving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “e.g.,” and “for example” set off lists ofone or more non-limiting examples, instances, or illustrations. Asutilized herein, a battery, circuitry or a device is “operable” toperform a function whenever the battery, circuitry or device comprisesthe necessary hardware and code (if any is necessary) or other elementsto perform the function, regardless of whether performance of thefunction is disabled or not enabled (e.g., by a user-configurablesetting, factory trim, configuration, etc.).

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A battery electrode, the electrode comprising: anelectrode coating layer on a current collector, the electrode coatinglayer comprising more than 50% silicon, wherein each material in theelectrode has a resistivity of less than 100 Ω-cm.
 2. The electrodeaccording to claim 1, wherein each material in the electrode has aresistivity of less than 10 Ω-cm.
 3. The electrode according to claim 1,wherein each material in the electrode has a resistivity of less than 1Ω-cm.
 4. The electrode according to claim 1, wherein each material inthe electrode has a resistivity of less than 1 mΩ-cm.
 5. The electrodeaccording to claim 1, wherein the electrode coating layer comprisespyrolyzed carbon.
 6. The electrode according to claim 1, wherein theelectrode coating layer comprises conductive additives.
 7. The electrodeaccording to claim 1, wherein the current collector comprises a metalfoil.
 8. The electrode according to claim 1, wherein the metal currentcollector comprises one or more of a copper, tungsten, stainless steel,and nickel foil in electrical contact with the electrode coating layer.9. The electrode according to claim 1, wherein the electrode coatinglayer comprises more than 70% silicon.
 10. The electrode according toclaim 1, wherein the electrode is in electrical and physical contactwith an electrolyte.
 11. The electrode according to claim 10, whereinthe electrolyte comprises a liquid, solid, or gel.
 12. The electrodeaccording to claim 1, wherein the battery electrode is in a lithium ionbattery.
 13. A method of forming an electrode, the method comprising:fabricating a battery electrode comprising an electrode coating layer ona current collector, the electrode coating layer comprising more than50% silicon, wherein each material in the electrode has a resistivity ofless than 100 Ω-cm.
 14. The method according to claim 13, wherein eachmaterial in the electrode has a resistivity of less than 10 Ω-cm. 15.The method according to claim 13, wherein each material in the electrodehas a resistivity of less than 1 Ω-cm.
 16. The method according to claim13, wherein each material in the electrode has a resistivity of lessthan 1 mΩ-cm.
 17. The method according to claim 13, wherein theelectrode coating layer comprises pyrolyzed carbon.
 18. The methodaccording to claim 13, wherein the electrode coating layer comprisesconductive additives.
 19. The method according to claim 13, wherein thecurrent collector comprises a metal foil.
 20. The method according toclaim 13, wherein the metal current collector comprises one or more of acopper, tungsten, stainless steel, or nickel foil in electrical contactwith the electrode coating layer.
 21. The method according to claim 13,wherein the electrode coating layer comprises more than 70% silicon. 22.The method according to claim 13, wherein the electrode is in electricaland physical contact with an electrolyte and the electrolyte comprises aliquid, solid, or gel.
 23. The method according to claim 13, wherein thebattery electrode is in a lithium ion battery.
 24. A battery, thebattery comprising: a cathode, a separator, an electrolyte, and ananode, the anode comprising an electrode coating layer on a currentcollector, the electrode coating layer comprising a pyrolyzed carbon,conductive additives, and more than 50% silicon, wherein each materialin the electrode has a resistivity of less than 100 Ω-cm.